1. Field of the Invention
The present invention relates to an electrophotographic photoreceptor in which an undercoating layer and a photosensitive layer are formed in this order on a conductive support, and a method for producing the same. It also relates to a coating liquid for the photosensitive layer and a method for producing the same, and moreover, it relates to an image-forming apparatus using the electrophotographic photoreceptor.
2. Description of the Related Art
An electrophotographic process applicable to an image-forming apparatus such as copier and printer, is one of data-recording techniques utilizing photoconductive phenomena of a photoreceptor. In such an image-forming apparatus as digital-type copier, an image is formed by means of reversal development. That is, an image is formed by the steps of charging the surface of the photoreceptor uniformly by means of corona discharge in a dark place, then selectively discharging a certain region exposed to light to form a latent image, then depositing colored and charged particles (toner) on the latent image to form a visible image, and then transferring the toner onto a prefixed sheet of paper to fix and form an image thereon. The basic properties required for the photoreceptor are as follows. To be uniformly chargeable up to a desired level of the potential in a dark place, to have a high electric charge-holding capacity in a dark place with a lower electric discharge, and to have a high photosensitivity to rapidly discharge in response to photo-irradiation. It is also required for the photoreceptor that the electrostatic charge is easily removed and the residual potential is lower; that it is superior in mechanical strength and flexibility; that there is no fluctuation in the electric properties such as chargeability, photo-sensitivity, residual potential, and the like, even after repeated use; and that it is highly durable to heat, light, temperature, humidity, ozone deterioration, and the like. The photoreceptor for which such high stability and durability are required includes a monolayer type of which the photosensitive layer is composed of a charge-generating material and a charge-transporting material in a monolayer, and a multilayer type (function-separating type) which is made by laminating a charge-generating layer containing a charge-generating material and a charge-transferring layer containing a charge-transferring material.
On the other hand, in an image-forming apparatus in recent years, functional improvements such as improvement of image quality by image processing, maintaining high quality of image and image processing, and a combination with a facsimile apparatus, etc., have been attempted. Moreover, functional improvements for the photoreceptor has also been investigated. For example, improvement of image quality by reducing image defects has been investigated. Since toner deposits on a surface region of the photoreceptor on which the charges have been reduced by exposure to light, when the charge is reduced by other factor than exposure to light, image defects such as fogs, so-called black spots (very small dark spots), occur to decrease the image quality. In order to reduce such image defects, an undercoating layer is provided. In fact, an undercoating layer that works as a charge-blocking layer is provided between a conductive support and a photosensitive layer. Injection of a carrier from the conductive support microscopically erases or reduces the surface charge to produce image defects. However, the defects on the surface of the support are covered with the undercoating layer provided, which improves the chargeability, enhances adhering and coating properties of the photosensitive layer, and reduces the carrier injection from the support. Therefore, it is possible to prevent occurrence of image defects.
Moreover, an attempt to attain high sensitivity has been done. In fact, phthalocyanine pigments have been used as charge-generating materials contained in the photosensitive layer, particularly charge-generating layer. In an image-forming apparatus for digital-processing image data, a light source such as laser beams or LED (light emitting diode) is used for exposure to light, wherein the photoreceptor has to show high sensitivity at a relatively long wavelength range of approximately 620 nm-800 nm. Although there are phthalocyanine pigments and trisazo dyes as charge-generating materials therefor, a particularly highly sensitive and chemically stable phthalocyanine pigments are employed.
In the undercoating layer provided for improving the image quality by reducing the image defects, a variety of resin materials have been employed. For example, a polyamide resin is used in Japanese Unexamined Patent Publication JP-A 48-47344 (1973), but when the undercoating layer is constructed only with a resin material, accumulation of the residual potential becomes large to decrease sensitivity. This tendency is remarkable under an environment of lower temperature and lower humidity. Moreover, in Japanese Unexamined Patent Publication JP-A 56-52757 (1981), it contains titanium oxide, and in Japanese Unexamined Patent Publication JP-A 11-15184 (1999) it contains a coupling agent having an unsaturated linkage. Furthermore, in U.S. Pat. No. 5,489,496, an undercoating layer containing needle crystals with a particular resistance value is provided, and in U.S. Pat. No. 5,391,448 the content of titanium oxide and the film thickness in the undercoating layer are optimized. The so far known photoreceptor using such an undercoating layer, however, is insufficient in its characteristics, and further improvement is desired.
In order to attain high sensitivity, a phthalocyanine pigment is contained in the photosensitive layer, particularly charge-generating layer. The particle size of phthalocyanine pigments has an influence on the image quality, and in order to prevent image defects, it is necessary to make the particle size 1 xcexcm or less in the prior art photoreceptor. The photosensitive layer and the charge-generating layer may be prepared by using a coating liquid which is prepared by dissolving a binder resin material and dispersing a phthalocyanine pigment therein, wherein the phthalocyanine pigment is dispersed into the coating liquid until particle size becomes 1 xcexcm or less. In this connection, the phthalocyanine pigments exists in various crystal forms, and the dispersion time of the phthalocyanine pigment affects the crystal forms, so that when the crystal is dispersed to 1 xcexcm or less in particle size the crystal form is changed to decrease the sensitivity. Moreover, when the dispersion time is prolonged, the sensitivity decreases due to contamination of impurities from the dispersing media. In Japanese Unexamined Patent Publication JP-A 3-221963 (1991), there is disclosed a charge-generating layer containing a phthalocyanine pigment, in which the content of large-sized particles with the average particle size of 1 xcexcm or larger is made 10% by volume or lower in particle size distribution, using a technique for removing large-sized particles by centrifugation or filtration after dispersion of the phthalocyanine pigment. The content of large-sized particles with the average particle size of 1 xcexcm or larger over 10% by volume or higher, is not preferable because image defects are produced.
An object of the invention is to provide an electrophotographic photoreceptor capable of forming an image of high quality owing to its high sensitivity and reduced image defects, and a method for producing the same, to provide an coating liquid for a photosensitive layer and a method for producing the same, and moreover to provide an image-forming apparatus using such an electrophotographic photoreceptor.
The invention provides an electrophotographic photoreceptor comprising a conductive support, an undercoating layer formed on the conductive support, and a photosensitive layer formed on the undercoating layer, wherein
the undercoating layer contains titanium oxide particles in at least either needle shape or dendrite shape, and
the photosensitive layer contains a charge-generating material of which primary particle size and cohesive particle size are in a range of from 0.01 xcexcm to 10 xcexcm.
According to the invention, the photoreceptor is constructed by forming an undercoating layer on a conductive support, which layer contains titanium oxide particles in at least either needle shape or dendrite shape, and then forming a photosensitive layer on the undercoating layer, which photosensitive layer contains a charge-generating material of which primary particle size and cohesive particle size are in a range of from 0.01 xcexcm to 10 xcexcm. In such a photoreceptor, high sensitivity and durability can be attained, and less defective image can be formed.
When the content of titanium oxide is low in the undercoating layer, for example, when the content of titanium oxide is lower than that of a binder resin, the volume resistance of the undercoating layer becomes larger to block transportation of a carrier produced by exposure to light and enhance the residual potential. Moreover, in repeated use, the residual potential accumulates, and the accumulation is remarkable under low humidity to decrease durability. With increase of the titanium oxide content, such an inconvenience is reduced, but in using repeatedly for a long period of time, the residual potential tends to accumulate, and particularly it is remarkable at low humidity. On the other hand, when the binder resin is almost exhausted, the coat strength of the undercoating layer is decreased, and the adhering property with the support is also decreased. When such a photoreceptor is used repeatedly, the undercoating layer is ruptured to decrease sensitivity and image quality. Moreover, the volume resistance of the photoreceptor rapidly drops to decrease chargeability, and carrier injection from the support takes place easily to produce image defects. Thus, mere addition of titanium oxide to the undercoating layer does not give sufficient characteristics. In the invention, since the undercoating layer contains the titanium oxide in at least either needle shape or dendrite shape, it is possible to reduce accumulation of the residual potential and suppress the carrier injection from the support to prevent occurrence of image defects. Additionally, durability in repeated use is enhanced.
Moreover, the particle size of the charge-generating material contained in the photosensitive layer has great effect on the image quality. In this connection, the particle size means the size (diameter) of primary particles or of cohesive particles. The primary particle size means the minimum particle size to maintain a crystal form of the charge-generating material, and the particles having such size are called primary particles. When dispersion (grinding of particles) is advanced, cohesive power is increased to give a well-dispersed coating fluid of which the dispersion is well under way in appearance. At this point, the charge-generating material stably exists not only in a state of primary particles but also in that of cohesive particles that are formed by cohesion of several primary particles. The cohesive particle size means the size (diameter) of such cohesive particles. When the primary or cohesive particle size is larger than 10 xcexcm, coating homogeneity of the photosensitive layer is lost to produce nonuniformity of the image and yield many black spots decreasing the image quality. In the invention, homogeneity of the photosensitive layer is improved to give a less defective image since it contains the charge-generating material of which the primary and cohesive particle size is in a range of from 0.01 xcexcm to 10 xcexcm. Thus, such a combination of the photosensitive layer and the undercoating layer can afford a photoreceptor which has high sensitivity and durability and can form an image of high quality.
According to the invention, the undercoating layer formed on a conductive support contains titanium oxide particles in at least either needle shape or dendrite shape, and the photosensitive layer formed or the undercoating layer contains a charge-generating material of which the primary and cohesive particle size is in a range of from 0.01 xcexcm to 10 xcexcm, so that high sensitivity and excellent durability are attained and less defective images can be formed.
Moreover, in the invention it is preferable that the photosensitive layer has a multilayer structure comprising a charge-generating layer and a charge-transporting layer, and the charge-generating material is contained in the charge-generating layer.
According to the invention, the photoreceptor is of multilayer type, and the undercoating layer in the photoreceptor of multilayer type contains titanium oxide particles in at least either needle shape or dendrite shape, and the charge-generating layer contains a charge-generating material of which primary and cohesive particle sizes are in a range of from 0.01 xcexcm to 10 xcexcm. Thus, accumulation of residual potential is reduced to give high sensitivity and excellent durability. Moreover, less defective images can be formed.
Moreover, according to the invention, even in the case of the multilayer structure comprising a charge-generating layer and a charge-transporting layer, high sensitivity and excellent durability can be obtained and a less defective image can be formed.
Moreover, in the invention it is preferable that the charge-generating material is a phthalocyanine pigment.
According to the invention, the use of a highly sensitive and chemically stable phthalocyanine pigment can afford a less defective image. Since a phthalocyanine pigment is used, high sensitivity can be obtained in a relatively long wavelength range of approximately 620 nm-800 nm in an image-forming apparatus using a light source such as laser beams, LED, and the like.
Because the crystal form of the phthalocyanine pigment influences the sensitivity, a coating fluid for a photosensitive layer which is prepared by dispersing a phthalocyanine pigment under such a relatively mild condition as the crystal form is not changed, is used to form a photosensitive layer. However, the processing under a mild condition leaves large-sized particles in the suspension, which produces image defects. In the photoreceptor of the invention, since the particle size of phthalocyanine pigment is optimized and such a photosensitive layer is combined with an undercoating layer containing titanium oxide particles in at least either needle shape or dendrite shape, a less defective image with a high sensitivity can be formed.
Moreover, according to the invention, the use of a phthalocyanine pigment as a charge-generating material can afford images with no defect. In addition, since a phthalocyanine pigment is used, high sensitivity can be obtained in a relatively long wavelength range of approximately 620 nm-800 nm in an image-forming apparatus using a light source such as laser beams, LED, and the like.
Moreover, in the invention it is preferable that a surface of the titanium oxide particles is coated with at least either aluminum oxide or zirconium oxide.
According to the invention, the undercoating layer contains titanium oxide particles of at least either needle shape or dendrite shape, of which the surface is coated with any of aluminum oxide, zirconium oxide, and a mixture thereof, and so occurrence of image defects can be prevented.
The titanium oxide particles so far used in an undercoating layer are in a granular form. Under observation with an electron microscope, the granular titanium oxide is slightly uneven but nearly globular particles in a range of from 0.01 xcexcm to 1 xcexcm in particle size, of which the average aspect ratio is in a range of from 1 to 1.3. When the undercoating layer contains the granular titanium oxide particles, the contact between the particles becomes nearly point contact, in which the contact area is so small that the resistance of the undercoating layer is high, the characteristics of the photoreceptor, particularly the sensitivity is low, and the residual potential is high, until the content of the titanium oxide particles exceeds a certain level. When the content of the titanium oxide particles is increased, however, the charge-blocking function in the undercoating layer is decreased to produce image defects. Moreover, the dispersibility and preservative stability in the coating liquid for forming the undercoating layer are decreased, and the coating strength of the undercoating layer or the contact capability is decreased to produce image defects.
Since the photoreceptor of the invention contains the titanium oxide particles in at least either needle shape or dendrite shape, which is coated with at least one of aluminum oxide and zirconium oxide, the dispersibility and preservative stability of the coating liquid can be retained at a high level, even though the titanium oxide is dispersed therein at a high content. Thus, the defects of the support can be covered to form a uniform undercoating layer, and a uniform photosensitive layer can be formed on such undercoating layer to form a less defective image. Moreover, the charge-blocking function of the undercoating layer is improved to prevent occurrence of image defects.
Moreover, according to the invention, the surface of the titanium oxide particles is coated with at least one of aluminum oxide, zirconium oxide, and a mixture thereof, so that occurrence of image defects can be prevented.
Moreover, in the invention it is preferable that a surface of the titanium oxide particle is coated with at least one of silane coupling agent, silylating agent, titanate-type coupling agent and aluminum-type coupling agent.
According to the invention, since the undercoating layer contains the titanium oxide particles in at least either needle shape or dendrite shape, which is coated with at least one of silane coupling agent, silylating agent, titanate-type coupling agent and aluminum-type coupling agent, the dispersibility and preservative stability of the coating liquid can be retained at a high level. Thus, occurrence of image defects as mentioned above can be prevented.
Moreover, according to the invention, since the surface of the titanium oxide-particle is coated with at least one of silane coupling agent, silylating agent, titanate-type coupling agent and aluminum-type coupling agent, occurrence of image defects can be prevented.
Moreover, in the invention it is preferable that mode sizes of primary particles and cohesive particles in the phthalocyanine pigment are selected in a range of from 0.01 xcexcm to 5 xcexcm.
According to the invention, for example, the selection of the mode size of the primary particles and cohesive particles in the phthalocyanine pigment in a range of from 0.01 xcexcm to 5 xcexcm enhances dispersion homogeneity of the phthalocyanine pigment to reduce occurrence of image defects. When a phthalocyanine pigment is used as a charge-generating material, it is difficult to disperse homogeneously the pigment because it forms a stable crystal form, and the presence of large-sized particles is prone to yield image defects. Moreover, excessive dispersion makes the particles so small to decrease the sensitivity. In the invention, when the particle size of the phthalocyanine pigment is selected in the afore-mentioned range, a uniform photosensitive layer can be obtained to prevent occurrence of image defects.
Moreover, image nonuniformity and decrease of the sensitivity can be prevented by selecting the thickness of the charge-generating layer in a range of from 0.2 xcexcm to 10 xcexcm. The thickness of the charge-generating layer has effect on sensitivity, and so it is necessary to keep a certain extent of thickness in order to obtain a sufficient sensitivity. Formation of a uniform thickness, however, is difficult because it is much effected by various factors such as concentration of solid portion and viscosity in the coating fluid, boiling point of the solvent used, and the like. Increase of the concentration of solid portion makes homogeneous dispersion of the pigment difficult to leave large-sized particles, by which a uniform charge-generating layer cannot be formed to produce image defects. In order to obtain sufficient sensitivity and reduce image defects, it is necessary to keep definitely a matching between the particle size of the phthalocyanine pigment contained in the coating liquid and the thickness of the charge-generating layer. In the invention, the above-mentioned option of the range for the thickness of the charge-generating layer affords high sensitivity and prevents occurrence of image defects.
Moreover, according to the invention, by selecting the mode sizes of the primary particles and cohesive particles in the phthalocyanine pigment in a range of from 0.01 xcexcm to 5 xcexcm, dispersion homogeneity of the phthalocyanine pigment is enhanced to reduce occurrence of image defects.
Moreover, in the invention it is preferable that the phthalocyanine pigment is contained in the photosensitive layer in a range of from 10% by weight to 99% by weight.
According to the invention, by selecting the rate of the phthalocyanine pigment to the photosensitive layer in a range of from 10% by weight to 99% by weight, decrease of the sensitivity can be prevented. Further decrease of the dispersibility and preservative stability of the coating liquid can also be prevented. The content of the phthalocyanine pigment in the photosensitive layer or charge-generating layer has an effect on sensitivity. Particularly, when a coating liquid for forming the charge-generating layer is prepared by dispersion and then large-sized particles are removed, the content of the phthalocyanine pigment in the coating liquid falls off to decrease sensitivity. Moreover, the high content of the pigment decreases dispersibility and preservative stability of the coating liquid. In the invention, the option of the range for the content of the phthalocyanine pigment affords high sensitivity and prevents decrease of the dispersibility and preservative stability of the coating liquid.
Moreover, according to the invention, the phthalocyanine pigment is contained in the photosensitive layer in a range of from 10% by weight to 99% by weight, so that decrease of the sensitivity can be prevented. Furthermore, decrease of the dispersibility and preservative stability of the coating liquid can also be prevented.
Moreover, the invention relates to an image-forming apparatus utilizing reversal development, comprising the above-mentioned electrophotographic photoreceptor.
According to the invention, a less defective image can be formed. In the conventional photoreceptor installed on a digital-type image-forming apparatus, it is difficult to retain the crystal form of the charge-generating material such as phthalocyanine pigment consistent with fine granulation. Moreover, preservative stability of the coating liquid is worse. Accordingly, the sensitivity is decreased, and image defects are produced due to large-sized particles. In the image-forming apparatus of the invention, the photoreceptor as mentioned above is installed. Consequently, it is possible to provide an image-forming apparatus that produces an image with no defect such as black spots that occur in the usual reversal development.
Moreover, according to the invention, the electrophotographic photoreceptor is installed on the image-forming apparatus employing the reversal development method to form a less defective image.
Moreover, the invention provides a coating liquid for forming a photosensitive layer, comprising a binder resin for the photosensitive layer, an organic solvent for dissolving the binder resin, and a phthalocyanine pigment dispersed in an organic solvent, wherein mode sizes of primary particles and cohesive particles in the phthalocyanine pigment are selected in a range of from 0.01 xcexcm to 10 xcexcm.
According to the invention, the selection of the mode sizes of the primary particles and cohesive particles in the phthalocyanine pigment in a range of from 0.01 xcexcm to 10 xcexcm enhances dispersion homogeneity of the phthalocyanine pigment in the coating liquid for forming the photosensitive layer. In an image-forming apparatus equipped with the electrophotographic photoreceptor having a photosensitive layer formed of such a coating fluid, an image with less image defects can be formed.
Since the crystal form of the phthalocyanine pigment has an effect on the sensitivity, though the phthalocyanine pigment is dispersed under a relatively mild condition, large-sized particles remain to yield image defects. In the coating liquid for forming the photosensitive layer of the invention, occurrence of image defects can be prevented since it contains a charge-generating material of which the primary particle size and cohesive particle size are in a range of from 0.01 xcexcm to 10 xcexcm.
Moreover, according to the invention, the mode size of the primary particles and cohesive particles in the phthalocyanine pigment are selected in a range of from 0.01 xcexcm to 5 xcexcm, so that dispersion homogeneity of the phthalocyanine pigment can be enhanced. In an image-forming apparatus equipped with the electrophotographic photoreceptor having a photosensitive layer formed, of such a coating fluid, a less defective image can be formed.
Moreover, in the invention it is preferable that a content of primary particles and cohesive particles having a particle size larger than 5 xcexcm is 50% by weight or less of the phthalocyanine pigment.
According to the invention, the content of the primary particles and cohesive particles having a particle size larger than 5 xcexcm is fixed at 50% by weight or less of the whole pigment, so that dispersion homogeneity of the phthalocyanine pigment in the coating liquid for forming the photosensitive layer can be enhanced to form a less defective image.
Moreover, according to the invention, the coating liquid for forming the photosensitive layer contains the phthalocyanine pigment having 50% by weight or less primary particles and cohesive particles having a particle size larger than 5 xcexcm of the whole pigment particles, but no particles having a particle size larger than 10 xcexcm, so that dispersion homogeneity of the phthalocyanine pigment in the coating liquid for the photosensitive layer can be further enhanced to form a less defective image.
Moreover, the invention provides a method for producing a coating liquid for a photosensitive layer, comprising a step of dissolving a binder resin for the photosensitive layer in an organic solvent and a step of adding and dispersing a phthalocyanine pigment into the organic solvent in which the binder resin has been dissolved,
wherein the phthalocyanine pigment is dispersed until mode sizes of primary particles and cohesive particles of the phthalocyanine pigment fall in a range of from 0.01 xcexcm to 5 xcexcm.
According to the invention, the phthalocyanine pigment is dispersed until the mode sizes of the primary particles and cohesive particles of the phthalocyanine pigment fall in a range of from 0.01 xcexcm to 5 xcexcm, so that the dispersion homogeneity of the phthalocyanine pigment in the coating liquid for the photosensitive layer is enhanced, and thus a less defective image can be formed. In addition, it is possible to gain high working efficacy, productivity and reproducibility of the coating liquid, and further to prepare a coating liquid within a relatively short period of time. It is also advantageous in production cost.
Moreover, according to the invention, a binder resin for the photosensitive layer is dissolved in an organic solvent, a phthalocyanine pigment is added into the organic solvent in which the binder resin has been dissolved, and the mixture is dispersed until the mode sizes of the primary particles and cohesive particles of the phthalocyanine pigment fall in a range of from 0.01 xcexcm to 5 xcexcm, yielding the coating liquid for forming the photosensitive layer. Thus, the dispersion homogeneity of the phthalocyanine pigment in the coating liquid for the photosensitive layer is enhanced, and thus a less defective image can be formed. Furthermore, the coating liquid for the photosensitive layer can be prepared within a relatively short period-of time without spoiling working efficacy, productivity and reproducibility of the coating liquid.
Moreover, in the invention it is preferable that the method comprises the step of removing primary particles and cohesive particles having a particle size larger than 10 xcexcm of the phthalocyanine pigment, by filtration through a filter after the dispersion step.
According to the invention, the phthalocyanine pigment is dispersed until the mode sizes of the primary particles and cohesive particles fall in a range of from 0.01 xcexcm to 5 xcexcm, and the particles having a particle size larger than 10 xcexcm are filtered off through a filter, so that the dispersion homogeneity of the phthalocyanine pigment in the coating liquid for the photosensitive layer is further enhanced, and a less defective image can be formed.
Moreover, according to the invention, as the phthalocyanine pigment is dispersed until the mode sizes of the primary particles and cohesive particles fall in a range of from 0.01 xcexcm to 5 xcexcm, and the particles having a particle size larger than 10 xcexcm are filtered off through a filter, the dispersion homogeneity of the phthalocyanine pigment in the coating liquid for the photosensitive layer is further enhanced, and a less defective image can be formed.
Moreover, the invention provide a method for producing a photoreceptor, comprising a step of forming an undercoating layer on a conductive support and a step of forming a photosensitive layer on the undercoating layer, wherein in the step of forming the undercoating layer, an undercoating layer containing titanium oxide in at least either needle shape or dendrite shape is formed, and in the step of forming the photosensitive layer, a binder resin for the photosensitive layer is dissolved in an organic solvent, a phthalocyanine pigment is dispersed into the organic solvent, in which the binder resin has been dissolved, until mode sizes of primary particles and cohesive particles of the pigment fall in a range of from 0.01 xcexcm to 5 xcexcm, and the photosensitive layer is formed by a dip coating method with the resulting coating liquid for the photosensitive layer.
According to the invention, an undercoating layer containing titanium oxide in at least either needle shape or dendrite shape is formed on a conductive support, and then a photosensitive layer is formed on the undercoating layer. The photosensitive layer may be formed with a coating liquid which contains a binder resin, an organic solvent dissolving the binder resin, and a phthalocyanine pigment dispersed in an organic solvent, wherein the phthalocyanine pigment is selected so that the mode sizes of the primary particles and cohesive particles fall in a range of from 0.01 xcexcm to 5 xcexcm.
Since the photoreceptor is prepared with a coating liquid having high dispersion-homogeneity of a phthalocyanine pigment, a highly uniform photosensitive layer can be obtained. The photoreceptor produced by the production method of the invention can form a highly sensitive and less defective image. In the production method of the invention, such a photoreceptor can be produced in high productivity.
According to the invention, the photoreceptor is produced by forming an undercoating layer containing titanium oxide, which is in at least either needle shape or dendrite shape, on a conductive support, and forming a photosensitive layer on the undercoating layer with a coating liquid for the photosensitive layer as mentioned above by a dip coating method. Since a coating liquid for the photosensitive layer having high dispersion-homogeneity of a phthalocyanine pigment is used to produce the photoreceptor, a highly uniform photosensitive layer can be produced. The photoreceptor produced by the production method of the invention can produce a highly sensitive and less defective image. In the production method of the invention, such a photoreceptor can be produced in high productivity.
Moreover, in the invention it is preferable that, in the step of forming the photosensitive layer, a coating liquid containing a phthalocyanine pigment is used, wherein a content of 50% by weight or lower primary particles and cohesive particles having a particle size larger than 5 xcexcm is 50% by weight or less of the phthalocyanine pigment, and there is no particle having a particle size larger than 10 xcexcm in the the phthalocyanine pigment.
According to the invention, the content of 50% by weight or lower primary particles and cohesive particles having a particle size larger than 5 xcexcm is 50% by weight or less of the phthalocyanine pigment, and there is no particle having a particle size larger than 10 xcexcm in the the phthalocyanine pigment. Since the coating liquid for the photosensitive layer having high dispersion-homogeneity of a phthalocyanine pigment is used to produce the photoreceptor, a highly uniform photosensitive layer can be produced. The photoreceptor produced by the production method of the invention can produce a highly sensitive and less defective image. In the production method of the invention, such a photoreceptor can be produced in high productivity.
Moreover, according to the invention, the photoreceptor is produced by forming an undercoating layer containing titanium oxide, which is in at least either or needle shape and dendrite shape, on a conductive support, and forming a photosensitive layer on the undercoating layer with a coating liquid for the photosensitive layer as mentioned above by a dip coating method. Since a coating liquid for the photosensitive layer having high dispersion-homogeneity of a phthalocyanine pigment is used to produce the photoreceptor, a highly uniform photosensitive layer can be produced. The photoreceptor produced by the production method of the invention can produce a highly sensitive and less defective image. In the production method of the invention, such a photoreceptor can be produced in high productivity.
Moreover, in the invention it is preferable that in the step of forming the photosensitive layer, a coating liquid for forming the photosensitive layer is produced by dissolving a binder resin in an organic solvent, dispersing a phthalocyanine pigment therein, and filtering the organic solvent to remove the primary particles and cohesive particles having a particle size larger than 10 xcexcm of the phthalocyanine pigment.
According to the invention, in the photosensitive layer formed as mentioned above, particularly the coating liquid is filtered through a filter to remove the primary particles and cohesive particles having a particle size larger than 10 xcexcm of the phthalocyanine pigment. Since a coating liquid having high dispersion-homogeneity of a phthalocyanine pigment is used to produce the photoreceptor, a highly uniform photosensitive layer can be produced. The photoreceptor produced by the production method of the invention can produce a highly sensitive and less defective image. In the production method of the invention, such a photoreceptor can be produced in high productivity.
Moreover, according to the invention, the photoreceptor is produced by forming an undercoating layer containing titanium oxide, which is in at least either needle shape or dendrite shape, on a conductive support, and forming a photosensitive layer on the undercoating layer with a coating liquid for the photosensitive layer prepared as mentioned above by a dip coating method. Since a coating liquid for the photosensitive layer having high dispersion-homogeneity of a phthalocyanine pigment is used to produce the photoreceptor, a highly uniform photosensitive layer can be produced. The photoreceptor produced by the production method of the invention can produce a highly sensitive and less defective image. In the production method of the invention, such a photoreceptor can be produced in high productivity.